For many years research supported by this grant focused on how the master regulatory gene Sex-lethal (Sxl) functions in the development of sexual dimorphism in D. melanogaster. Two problems were of primary interest. The first was understanding the role of Sxl in selecting the appropriate sexual development pathway. The second was understanding how Sxl ensures that pathway choice is remembered and properly executed. While these issues remain central, the scope of our research has broadened into other areas over last few years because we followed up novel leads that came from our Sxl experiments. One of the new areas of interest is the development of the germline in the early embryo. Here we have focused on two related issues. The first is transcriptional quiescence in newly formed pole cells, while the second is the migration of the germ cells to the somatic gonad. Our studies on these two problems have allowed us to explore issues that are of perhaps more general significance than the precise mechanisms of sex determination in Drosophila. On the other hand, though these two aspects of germ line development are seemingly unrelated to Sxl, in both cases there are unexpected and interesting connections to Sxl. In fact, our studies on these two problems have provided new insights into how Sxl is regulated and uncovered novel functions for Sxl. During the upcoming grant period, we proposed to continue ongoing studies on Sxl and related aspect of germline development.